require_tree argument must be a directory in a Rails 5 upgraded app

Question

I just upgraded my app from Rails 4.2.7 to Rails 5.0.0.1. I used RailsDiff to make sure I had everything covered and I believe I did. So far everything has worked well up until the loading of my app.

Now I am seeing this error:

Sprockets::ArgumentError at /
require_tree argument must be a directory

This is my application.css:

/*
 * This is a manifest file that'll be compiled into application.css, which will include all the files
 * listed below.
 *
 * Any CSS and SCSS file within this directory, lib/assets/stylesheets, vendor/assets/stylesheets,
 * or any plugin's vendor/assets/stylesheets directory can be referenced here using a relative path.
 *
 * You're free to add application-wide styles to this file and they'll appear at the bottom of the
 * compiled file so the styles you add here take precedence over styles defined in any other CSS/SCSS
 * files in this directory. Styles in this file should be added after the last require_* statement.
 * It is generally better to create a new file per style scope. *
 *= require_tree .
 *= require_self
 */

This is my application.js

// This is a manifest file that'll be compiled into application.js, which will include all the files
// listed below.
//
// Any JavaScript/Coffee file within this directory, lib/assets/javascripts, vendor/assets/javascripts,
// or any plugin's vendor/assets/javascripts directory can be referenced here using a relative path.
//
// It's not advisable to add code directly here, but if you do, it'll appear at the bottom of the
// compiled file. JavaScript code in this file should be added after the last require_* statement.
//
// Read Sprockets README (https://github.com/rails/sprockets#sprockets-directives) for details
// about supported directives.
//
//= require jquery
//= require jquery_ujs
//= require turbolinks
//= require_tree .

This is what the server log looks like:

Started GET "/" for ::1 at 2016-09-02 09:08:19 -0500
  ActiveRecord::SchemaMigration Load (1.5ms)  SELECT "schema_migrations".* FROM "schema_migrations"
  User Load (1.7ms)  SELECT  "users".* FROM "users" WHERE "users"."id" = $1 ORDER BY "users"."id" ASC LIMIT $2  [["id", 2], ["LIMIT", 1]]
Processing by ProfilesController#index as HTML
  Rendering profiles/index.html.erb within layouts/application
  Profile Load (1.6ms)  SELECT "profiles".* FROM "profiles"
  Rendered profiles/index.html.erb within layouts/application (45.8ms)
Completed 500 Internal Server Error in 367ms (ActiveRecord: 6.3ms)


DEPRECATION WARNING: #original_exception is deprecated. Use #cause instead. (called from initialize at /.rvm/gems/ruby-2.3.1@myapp/gems/better_errors-2.1.1/lib/better_errors/raised_exception.rb:7)
DEPRECATION WARNING: #original_exception is deprecated. Use #cause instead. (called from initialize at /.rvm/gems/ruby-2.3.1myapp/gems/better_errors-2.1.1/lib/better_errors/raised_exception.rb:8)

Sprockets::ArgumentError - require_tree argument must be a directory:
  sprockets (3.7.0) lib/sprockets/directive_processor.rb:182:in `rescue in block in process_directives'
  sprockets (3.7.0) lib/sprockets/directive_processor.rb:179:in `block in process_directives'
  sprockets (3.7.0) lib/sprockets/directive_processor.rb:178:in `process_directives'

I am using no plugins of any kind. It is a fairly simple/vanilla app. The only styling is from the default scaffold.scss.

What could be causing this?

Answer 1

I finally figured it out. So because I am doing the upgrade, RailsDiff didn't tell me that I was missing something.

So the error message wasn't incorrect, however, what I forgot to do was to create an empty directory.

In my app/assets/javascripts/cable.js, I had the following:

//= require_tree ./channels

However, I forgot to actually create that folder.

So to fix this, all I had to do was create an empty folder within app/assets/javascripts called channels. Also, because git ignores empty directories, within that newly created folder, I also had to create an empty file called .keep.

So once I did the following, everything worked like a charm:

• Create folder: app/assets/javascripts/channels
• Create empty file within that folder: app/assets/javascripts/channels/.keep

Everything works perfectly now.